FIG. 1 is a diagram illustrating network connections of user terminals accessing a plurality of service server according to a conventional art.
NHN Corporation has provided a plurality of online game service such as Gostop, Hula, poker, Tetris, and chess, via NHN's own Hangame site. In FIG. 1, users using user PCs 101 and 102 access service servers 104, 105, and 106 providing an online game desired by users. For example, the service servers 104 and 105 may provide a Gostop game service, and the service server 106 may provide a Hula game service. In this case, login/logout of the user is separately performed by each of the service servers 104, 105, and 106, and login/logout information of the user is separately managed by the each of the service servers 104, 105, and 106. Accordingly, in a conventional technology, a user logged in to one service server does not know a present state of the user logged in to other service servers, for example, whether the user logs in or out or what game is being played by the user.
FIG. 2 is a diagram illustrating network connections of a location server for managing location information of users and service servers according to another conventional art.
To solve the problem of the configuration illustrated in FIG. 1, a location server 207 capable of collectively managing login/logout information of users in all service servers 204, 205, and 206 is provided. When users access service servers 204, 205, and 206 providing online games desired by users by using user PCs 201 and 202 via the Internet 203, service servers 204, 205, and 206 transmit the login/logout information of users to the location server 207. Accordingly, since the location server 207 collectively manages the login/logout information of users in service servers 204, 205, and 206, a state of users logged in to any service server may be provided to users.
However, currently, since online games provided by NHN Corporation are provided by several service servers, when managing login/logout information performed by the service servers in one location server, system loads on the location server becomes excessively heavy.
Accordingly, to alleviate the system loads concentrated on the location server, a replication group formed of location servers is provided. FIG. 3 is a diagram illustrating network connections of service servers, user terminals, and a plurality of location servers forming a replication group. The location servers belonging to the replication group must have the same state information in association with a login/logout state of a user.
However, as shown in FIG. 4, it is not guaranteed that a user login/logout message transmitted to location servers belonging to a replication group is transmitted to all location servers in the physically same sequence. FIG. 4 is a diagram illustrating messages transmitted to a plurality of location servers belonging to a replication group.
When users access service servers 304, 305, and 306 providing online games desired by users by using user PCs 301 and 302 via Internet 303, service servers 304, 305, and 306 transmit a user login/logout message to a location server 308 that is one of location servers 308, 309, 310, and 311 belonging to a replication group 307. The location server 308 receiving the user login/logout message transmits the user login/logout message to other location servers 309, 310, and 311 belonging to the replication group 307. However, it is not guaranteed that the transmitted user login/logout message is transmitted to all location servers in the same sequence.
For example, FIG. 4 illustrates messages transmitted to the location servers 308, 309, and 310 at a certain point in time. Login/logout messages 401, 402, and 403 are transmitted to the location server 308 at T1, T2, and T3, respectively. The message 401 indicates that a user AAA logs into a first channel of a game of Gostop. However, a message 411 indicating that the user AAA logs into the first channel of the Gostop game and a message 412 indicating that the user AAA logs out of the first channel of the Gostop game are transmitted to the location server 309. Also, although the location server 310 has the same number of messages as the location server 308, a sequence of the messages transmitted to the location server 308 is different from a sequence of the messages transmitted to the location server 310. Namely, the location server 308 receives the messages in a sequence of the message 401, message 402, and message 403, but the location server 310 receives the messages in a sequence of a message 421, message 422, and message 423. When the location servers 308, 309, and 310 determine a final login state of the user AAA according to the message finally received, the location server 308 determines the user AAA is logged into a fifth channel of a game of Hula, and the location server 309 and the location server 310 determine the user AAA logged out of the first channel of the Gostop game. Accordingly, present states determined by the location servers 308, 309, and 310 belonging to the replication group 307 are different from each other.
Accordingly, a method and system for enabling location servers belonging to one replication group to maintain the same state information though user login/logout messages that are transmitted to the location servers belonging to the replication group in a different sequence from each other is required.